My 15 gal tank has a variety of corals but only 2 tomato clowns each hosted by bubble tip anemones. I firmly believe that you shouldn't add more than 1 fish every other month so that the bacteria base can grow to handle the increased bio load. It has been 2 years since I've added fish. I found myself getting bored and decided to add another fish. After research, compatibility charts indicated that a puffer fish would get along with the existing clowns. I selected one at the LFS and monitored it for about a week to be sure it was healthy and then took him home. 2 days later, I found it dead in the filter. My water quality is excellent and I'm sure the Puffer was healthy. I'm guessing the two clowns killed it, even though there weren't any signs of trauma. I'm guessing it was a territorial issue as the puffer liked hanging in the rocks behind where the anemones and Clowns are. My Question: If Clowns and Puffers are compatible, and it was a territory issue how can I introduce new fish to the tank without them getting their butt kicked by the Clowns?